Wiper blades are generally molded in integral, parallel pairs, joined at a thin web. The web is later slit lengthwise, not simply to part the blades, but also to simultaneously produce a wiping edge or lip on each blade that is much cleaner and sharper than that which could be produced by molding the edge directly. The molded blade pairs are typically held in a fixture and slit apart by a sharp knife. This method works well so long as the blades are clamped correctly and the knife remains sharp. Unfortunately, as the knife inevitably dulls, edge quality deteriorates, so the process is inherently inconsistent.
Lasers have been used for some time to cut many different materials, including metal, wood, and various plastics, as well as rubber. Generally, when such materials are cut, the speed of the cut is of more significance than the condition of the edge. With a wiper blade, of course, the condition of the edge, which is the wiping lip of the blade, is all important. It must be smooth, straight and, sharp cornered in order to achieve good wipe quality in both wiping directions. Laser slitting of blades has been attempted following conventional methodology, which teaches that the focal point of the beam should be at or slightly below the surface of the material being cut. This has been found to produce a wiping edge with at least one rounded, non-sharp corner, which is unacceptable.